Vacuum drainage systems are generally known in which a vacuum source is used to transport waste fluid from a waste fluid generating source to a collection tank. In contrast to conventional plumbing, which uses gravity to collect and direct waste fluid, the vacuum source in such vacuum drainage systems creates a pressure differential across a discrete volume of waste fluid (also known as a plug or slug). Conventional vacuum drainage systems typically comprise a collection branch having an intake end open to atmosphere positioned below the waste fluid generating source for receiving the waste fluid. The waste fluid entering through the intake accumulates in a collection area under the force of gravity. A control valve selectively establishes fluid communication between the collection area and the vacuum source, thereby creating the pressure differential. Such systems conventionally have one or more tanks that are maintained under negative pressure by the vacuum source into which the slugs of waste fluid are transported. Additional valving and controls are needed to selectively empty the tanks into a final collection point, such as a municipal sewer system. While such vacuum drainage systems are generally suitable for a wide variety of applications, the collection tanks and associated valving and controls are overly complicated, and add to the expense of such a system.
A more simplified collection and discharge apparatus for use in a vacuum drainage system is described in U.S. patent application Ser. No. 4,246,925 to Oldfelt, which discloses the use of a generally vertical length of pipe having a vacuum source connected to an upper end of the pipe, while the lower end is open to atmosphere. The upper end of the pipe is connected by a conduit to a vacuum pump, while the lower end of the pipe is submerged into a tank that is partially filled with waste fluid. The vacuum pump generates a negative pressure in the vertical pipe, while the tank is maintained at atmospheric pressure. Waste fluid sources, such as toilets and sinks are connected to the vertical pipe by additional conduits, and waste fluid generated by these sources is transferred to the vertical pipe as discrete slugs, as described above. Due to the vacuum in the vertical pipe, the waste fluid is not immediately discharged from the vertical pipe but instead collects inside the pipe to form a liquid column. As the waste fluid accumulates, the liquid column obtains a mass which exceeds the vacuum force in the vertical pipe. Accordingly, waste fluid added to the top of the column beyond the vacuum force capacity causes a corresponding volume of fluid to be discharged from the bottom of the vertical pipe and into the tank. Thus, a substantially constant liquid column height is maintained inside the vertical pipe.
The vertical pipe disclosed in Oldfelt is generally suitable for applications having sufficient vertical clearance to house the vertical pipe. Any waste fluid sources must either be located above the vertical pipe or have runners extending vertically upward to tap into the upper end of the vertical pipe.
In such systems, it is important to prevent waste fluid from flowing into and flooding the vacuum source. Oldfelt discloses the use of a vertical pipe having a substantially uniform diameter, and the vacuum source conduit and waste fluid source conduit intersect the vertical pipe at points which are relatively near one another. Accordingly, a substantial risk exists in the Oldfelt apparatus that the waste fluid will flow into and flood the vacuum source.
It is also desirable for vacuum drainage systems to be capable of separately handling different types of waste fluid. Local plumbing codes often require black water (i.e., polluted liquid from toilets and urinals) to be treated or otherwise handled differently than other types of waste fluid before discharge into a sewer. In a supermarket, for example, various types of waste fluids are generated. Gray water, such as trade waste from meat preparation sinks, must often be directed through treatment apparatus before discharge into the sewer. Other relatively cleaner fluids, such as condensate from refrigerated cases, may often be released directly into the sewer, or may be reused on site to provide, for example, a source of toilet water. Oldfelt fails to disclose a single system capable of separately handling multiple types of waste fluid flows.